Screening apparatus



Dec. 4, 1928.

s. D. ROBINS scansume APPARATUS Filed mm '12, 1927- 4 Sheets-Sheet Dec. 4,1928. 1,693,940 S; D.- ROBINS SCREENING APPARATUS 4 Sheets-Shut 2' Dec. 4, 1928.

' S. D. ROBINS SCREENING APPARATUS Filed April 12, 192"! jjvsheezsheet f6; lib/Urg- Dec 4, 1928. 1,693,940

S. D. ROBINS SCREENING APPARATUS Filed Apr11 12, 1927 4 Sheets-Sheet I .9

Patented Dec; 4.192s.

UNITED STATES PATENT OFFICE.

SAMUEL DAVIS ROBINS, OF WOODMERE, NEW YORK, ASSIGNOR TO ROBINS CONVEY- ING BELT COMPANY, OF PASSAIO NEW JERSEY, A CORPORATION OF NEW JERSEY.

SCREENING APPARATUS.

Application filed April 12,

This invention relates to vibratory screens, such as are used for screening coke, crushed stone, ore, sand, gravel, etc., having especial reference to that class of screens wherein a rigid screening element of substantial weight is given a circular motion, or gyration, in planes at right angles to the plane of the screen surface.

' As is recognized in the screening art the effective gyratory motion of the screening element is variable in accordance with the character of the material that is being treated; that is to say, for fine screening a motion or vibration of small amplitude and high frequency is employed, Whereas for coarse screening, (in which the screen openings are, say, an inch or more in diameter), a motion of relatively large amplitude and low fre-- quency is used. In the screens of the prior art the construction and operation of the mechanism for actuating the heavy screening element is such that the movementof said element tends to set up unbalanced impulses that are transmitted to the supporting structure with destructive results. Even when the frequency of vibration of the screen is relatively low the floor spans and bracing commonly used in the structure have free periods of vibration in consonance with the vibration of the screen.

The principal object of my invention is to overcome the objections mentioned in a screen of the class referred to, by the provision of simple and efficient screen operating mecha-.

' nism, including eccentric and spring connections which are co-operatively related to effeet and maintain the dynamic balancing of the apparatus under all working conditions.

Another object of the invention isthe provision of means whereby the angle of the screen surface can be readily and quickly adjusted while the screen is in operation, and this withoutimpairing the balance of the apparatus.

\Vith these and other objects in view my invention comprises novel features of construction and principlesof operation which, in a preferred embodiment of the invention, will be hereinafter described, and the scope of the invention then be defined in the appended claims. w

In the drawings- Figure 1 is a side elevation of a'screen embodying the preferred form of my invention.

through the drive shaft and one of the counterweighted flywheels and adjuncts, as on the line 66 of Fig. 3.

Fig.7 is a perspective view of one of the clamps for securing the live screen frame to the gyratory carrier shaft. 1

Figs. 8 to 13, inclusive, are stress diagrams hereinafter considered.

Referring to the drawings, 10' designates a substantial base frame mounted on suitable supports (not shown), which frame, in a simple and eflicient form, consists of two spaced-apart flanged uprights 11 connected by cross-braces 12 of angle iron to providea rigid structure. Bolted to the uprights are bearings 13, preferably of the self-aligning roller type, in which are journaled the ends of a shaft 14 that is adapted to be driven from a suitable source of power. -Keyed on the shaft, adjacent the respective bearings 13, are fly wheels 15 having appropriate counl terweights 16, each wheel being-preferably made in two parts namely a hub portion 1 and an outer portion including the rim 18. The hub is bored to receive the adjacent end of :the shaft 14, concentrically with the rim 1 of the fly wheel, and an eccentric annular recess 19 is-formed between the hub and the rim. In this recess is mounted, for turning adjustment, a bushing 20 having an eccentric bore, the eccentricity whereof is the same as that of the recess 19 with relation to the concentric hub and rim of the fly wheel. Consequently by properly turning the bushing within the recess 19 the eccentricity of the bore of the bushing with relation to the drive shaft may be varied from zero to a value equal to the eccentricity of therecess plus that of I'the bushing. A suitably-disposed screw 21 in the wall of the recessengagesthe bushing justment,

.60 27, 29 of the live frame and engage the ad- Within the eccentric bore of the bushing is seated the outer race of a ball orroller hearing 22, the inner race of which is seated upon the. adjacent end of ,a hollow cylindrical shaft 23 which surrounds the drive shaft. (See Figs. 3 and 6.) Hence the rotation of the drlve shaft, with its fly wheels, causes the hollow shaft to travel in an eccentric path about the axis of rotation ofthe drive shaft, that is to say, the hollow shaft receives a gyratory motion in planes at right angles to the axis of the drive shaft. If desired a plain bushing may be used instead of the ball or roller bearing 22 referred to.

The counterweight 16- of each' of the fly wheels is preferably bolted to the web of the wheel in the space between the rim andthe hub, said weight comprising a number of separate pieces which may be secured in venous positions to meet balance require ments with different eccentric adjustments p of the bearing in the fly wheel.

Grease seals'24, which encircle the hollow shaft, are fastened to and may turn with the eccentric bushings 20. These seals prevent the escapeof lubricant from and the en- ,.Both the two u per side plates 27 and the trance of dirt to the bearin s.

An inclined screening. e ement is operatively connected, midway between its ends, to the hollow shaft 23 so as'to receive uniform gyratory motion therefrom, as will be hereinafter described, such shaft thus constituting in effect a carrier for the screening element. This screening element, in the form illustrated, comprises a rectan lar. live frame with tensloned screen clot s therein. In the present instance the live frame is composed of-two sections, one superposed on the other, fastened together by bolts 25, which sections are provided with spaced-apart screenin cloths 26. The upper section is compose of two side plates 27 having on their inner surfaces longitudinally extending reinforcing angle bars 28. The lower section, is com osed of two side plates 29, preferably in t e form of structural channels.

two lower side p ates 29 are rigidly connected at intervals bya number of angle bars 30,

each of which has aflixed thereto a vertical in order to prevent whippingi. Tension of the screen'cloths .is maintained, and they are kept in contact with the upwardly curving edges of the plates, by means of laterallydisposed grips 32 which engage the margins of the cloths. Screws 33 extend through suitably-disposed apertures in the side plates jacent cloth' grips, and. hencepas the nuts' sections of 'unequal'length, with the shorter section, a, at the high or feeding end of the screen overlapping the longer section, b,.

thus permitting the section at the feeding end to be readily removed and replaced when "worn, without disturbing or discarding the longer portion of the cloth which is still useful. (See Fig. 2.) J

The upper side plates 27 of the live frame have formed therein, midway between the ends of the structure, openings 35 through which the hollow shaft 23 extends. .This shaft is firmly fastened to the live frame by means, for example, of complemental clamp sections 36 (Fi '7) which tightly embrace the hollow sha t and are bolted to the adjacent side plates. Therefore the gyratory motion of the hollow shaft is positively. imparted to the live frame and all points of the latter are given a true circular motion in paths lying in planes at right. angles to the drive shaft; and, since the actuating center of the shaft coincides with the center of gravity of the frame, the inertia of the latthe actuatin center; it being obvious that if the actuating center were away from the ter as a whole does not set up moments about center of'gravity of the screening element,

such moments would be set up and would all points of the live frame. Such a motion .of'this frame, being a compound motion, is impossible to counterbalance effectually, with the result that the escapin vibrations influence the paths of motion described by.

would be disastrously transmitte to the supporting structure.

It is to be understood that the counterweights 16 of the fly wheels 18 arelocated, with relation to the axis of the drive shaft 14, diametrically op osite the central axis may attain time require, and also to ensure the fixed angular position of theframe under actual workifi conditions, irrespective of the tendency o the hollow shaft to rotate the live framein the direction of'movement of the drive. shaftorthe tendency" of 'the axis of the drive shaft are such that the running. a i

unequal loading of material on the screen-.

ing surface to set up moments tending to turn the frame in one direction or the other about" the drive shaft, spring supporting and controlling mechanism is arranged in co-operative relation to the live frame and the actuating devices therefor, which mechanism in its preferred form is as follows:

Supported by andbetween the uprights of the base frame is a pendant frame comprising two suitably spaced hanger plates 37 rigidly connected by parallel angle bars38. In the present instance the hanger plates are pivoted at their upper ends to the adjacent uprights 11 by means of bolts 39, and'the lower ends of such plates are secured to the uprights by. bolts 40 which extend from the plates through suitabl located arcuate slots 41 in the uprights. ence by loosening the nuts 42 of the bolts 40, the pendant frame can be laterally adjusted within limits to vary itsangu-larity in respect to the vertical, and then bytightening the nuts the said frame can be effectually secured in any desired position of adjustment. To facilitate the operation of ad'ustment, a shaft 43 is journaled in suitable oles in the hanger plates, the ends of which shaft extend through arcuateslots 44 in the respective plates. The shaft 43 has keyed thereon, between the hanger plates and the respective uprights 11, pinions 45 in mesh w th arcuate racks 46 which are integral with -or secured to the said uprights; and the shaft has also keyed thereon, at its outer ends, suitable actuating devices, as, for exanr ple, .hand cranks 47, whereby the shaft '43 may be turned from either sideof the apparatus, thus through the intermeshing action of the pinions and the racks effecting the desired adjustment of the pendant frame, and this while the screening apparatus is On the cross-bars .38 of the adjustable pendant frame, adjacent the respective side members of the latter, are supported two springs 48 which, in the presentlinstance, areof the leaf type. Thesesprings are securely clamped in their mid sections between horizontal plates 49 by suitable bolts 50, which bolts also serve to hold the springs securely to bedplates 51 that are, in turn, aflixed, as

i by rivets, to the cross-bars 38. (See Fig. 4.)

The respective ends of each spring .48 are flexibly connected by means-of parallel links 52 to brackets 53 on the lower section of the live frame, one link preferably depending and the other link upstanding, asshow'n, 'to accommodate the inclination of the live .frame. As thus mounted and connected to the live frame, the springs simultaneouslyexert an .upward resilient action against the frame in paths equally spaced from the respective sides of the actuating shaft. (See Fig.1.)

From the foregoing described construction it'will be seen'that the live frame and its associated spring supports are adjusted as a unitcoincident with the adjustments of the pendant. frame previously explained, and therefore the'springs resiliently maintain the live frame in any angular position of adjust- ,ment of the latter, and thiswithout impairng the resilient effect of the respective ends ing the centrifugal force setup by the gyrating live frame, viz a'force of uniform magnitude,-but changing in direction. The result-ant of thesetwo forces is a force changing both in direction and magnitude. By, employing the springs acting upwardly againstthe live frame as aforesaid, the re sultant force indicated is greatly reduced and in consequence the eccentric bearings and also the stationary bearings for the drive shaft are relieved of a large part of their maximum stress.

The upwardly acting springforce is a, va

riablc one, the magnitude of which changes With-each position of the eccentric, that is to say, the maximum is at the bottom of the stroke when the springs aremost deflected and the minimum is atthe top of the Stroke when the springsa're least deflected.

By reference to the diagrams, Figs. 8 to 13, inclusive, it will be seen that in a gyratory screening apparatus embodying my inve'ntion, the stresses on the'eccentric bearings 22 and on the main bearings 13 are reduced to a minimum, and that all forces are counteracted within the stationary base framelO to the exclusion of escaping impulses into the supporting structure.

In Fig. 8 are plotted the static forces, (*W,

S for eight positions of the eccentric 45 de- The arrows pointing upward grees apart.

are the Vector values of the varying spring force (S) while those pointing downward represent the constant force of gravity which'is equal to the-total weight of the live frame.

wheels.

In Fig. 9 are plotted the static resultants, it being noted thatthestatic forces are vertical becauselthe horizontal leaf springs produce only vertical reactions. Should the an-' plus the weight'of the shaft and fly gle of the screen be changed, the force diagram will be changed accordingly, but, for the sake of illustration, only the horizontal setting of the springs need be considered.

The gyration of the live frame sets up a centrifugal force (C) which has a constant value for a given eccentricity at any speed. This force is indicated in the diagram Fig.

. amount of eccentricity must be sufiicient to 10, asa radial force, constant in magnitude, but changing in direction at the rotational speed of the shaft, which speed for a given set up enou 'h centrifugal force to throw the material oil the screensurface at each-revolution. To fulfil this condition the centrifugal force must slightly exceed the accelerative force of gravity.

The diagram, Fi 11, indicates the, combined resultants of the static and kinetic forces acting upon the eccentric bearings for the eight different positions of the eccentric.

Fig. 12 is a polar diagram of the same resultant, and Fig. 13 is a similar diagram of the same system of forces if the spring element be omitted. A comparison ofthese two. diagrams shows that approximately of I the ma1!rimum-bearing stress has been elimiof the live frame.

nated from'the eccentric'bearings bythe provision of the spring element.

There are no kinetic forces acting on the main bearings 13 since the flywheel counterweights are'designed to balance the .weight Thus the centrifugal force acting upon the counterweights at all s eeds is equal in magnitude and opposite in irection to the centrifugal force acting upon-the live frame. Hence the introduction of the springs does not effect the maximum main bearing stress but serves to set up in the main bearings a fluctuating stress varying from zero to W with each revolution of the drive shaft. The main bearings, then, are free from all except static forces, which are indicated as combined in Fig. 9.

Since the main bearings are free from kinetic stresses as'above mentioned, they transmit-only static stresses to the base frame, the fluctuating downward 'force thus transmitted being indicated in Fig. 9.

The tension. in the hanger plates 37 which carry the springs 48, is a fluctuating stress,

being eatest at the bottom of the stroke, when t e springs are under greatest compression, and least at the top of the stroke when l the springs are under 1 ast compression.

- anced by It willbe noted from ig. 9 that the downward force transmitted by the main bearings is least at the bottom of the stroke and greatest at the top. Thus the fluctuating tension in the hanger plates is 180 degrees out of base with the fluctuating downward forces m the main bearings, with the result that the base frame transmits only a uniform downward force to its supports. s

From the foregoing it will be seen that (1) the resultant stresses are reduced about 40%; (2) the centrifugal stresses are balthe counterweights and are confined to the eccentric bearings, and (3) the base frame receives two series of counteracting stresses, thus precluding the escape of vlbrations into the supporting structure for the apparatus.

It is to be'understood that .myinvention is not limited to the particular construction herein disclosed,'as thesame may bevariously modified within the principle of the invention and 'the.s cope of the appended claims. i

Iclaim I q I r 1. A screening apparatus comprising a screen'frame, a drive-shaft substantiall co incident with the center of gravity 0 the said frame, stationary bearings for said shaft,

connections between said shaft and frame whereby the frame is positivelygyrated in circular paths lying in planes at right angles to the drive shaft, and resilient equalizing means simultaneously acting in'the same direction upon said frame beyond the respec'-- 'tive sides of the shaft and operative to maintain the said frame' constantly in correct screening position while permitting its positive gyration.

screen frame, a drive shaft substantially c0- incident with the centerof gravity of the said 2. A; screening apparatus comprismg a frame, stationary bearings for- :said shaft,

connections between said '-shaft a'nd frame whereby the frame is positively gyrated in circular paths lying in planes at right angles to the drive shaft, and resilient means coacting with said frame to exert upward force thereon simultaneously beyond the respecload upon the said drive shaft bearing is relieved and at the same time the said frame is tive sides of the shaft whereby the downward constantly maintained "in correct screening :1

position while permitting its positive gyration. 1

3. In a screening apparatus, a screen frame including a taut screening surface, actuating of gravityof the said frame, stationary concentric bearings for said shaft, eccentric hearings on said shaft, a member mounted in said eccentric beatings and fixed to the said frame, whereby the said frame is positively gyrated' in circular paths lying in planes at right angles to the drive'shaft', and sprin means exerting upward thrust on the sai frame simultaneously beyond the respective 4. In a'screening apparatus, a screen frame" 7 sides of the shaft to relieve the said concen-- trio and eccentric bearings of the load caused by the weight of said frame and to maintain the said frame constantly in correct screenlng position during its positive gyration.

5. A screening apparatus comprising a screen frame, a drive shaft substantially coincident with the center of gravity of the said frame, stationary bearings for said shaft, means, including an eccentric on the drive shaft and a connecting member between said the base frame close to the center of gravity of the screen frame, means, including an eccentric on the drive shaft anda connecting'memberbetween said eccentric and the central portion of the screen frame, whereby the said screen frame is gyrated at all points in circular paths lying in planes at right angles to the axis of the drive shaft, counterweights'cariied bythe drive shaft and rotating therewith to produce dynamic baiance, and resilient equalizing means interposed between the said screen frame and the stationary base frame and simultaneouslya'cting in the same direction upon said frame beyond the respective sides of the shaft to maintainthe said screen frame in correct screening position while permitting its positive gyration.

7. A screening apparatus comprising a screen frame, a-drive shaft havingits axis substantially coincident with the center'of gravity of said frame, stationary bearings for said shaft, annular bearings eccentric to and carried by said shaft, a hollow shaft freely,

encircling said drive shaft and supported in said annular bearings, said hollow shaft carrying the screen frame, whereby during the rotation of the drive shaft the said hollowshaft and frame are positively gyrated in circular paths lying in planes at right angles to the drive shaft, and resilient equalizing means simultaneously acting in the same direction upon said frame beyond the respective sides of the shaft and operative to main.-

tain the said frame constantly in correct screening position during its positive gyration.

8. A screening apparatus comprising a screen frame, a drive shaft having its axis substantially coincident with the'center of gravity of said frame, stationary bearings for said shaft, adjustable annular bearings eccentric to and carried by saidshaft, means for securing said annular bearings in predetermined positions of eccentric adjustment, a hollow shaft freely encircling said drive shaft and supported in said annular bearings, said hollow shaft carrying the screen frame, whereby during the rotation of the drive shaft the said hollow shaft and frame are positively gyrated in circular paths lying in planes at right angles to the drive shaft,

ly acting in the same direction upon said frame beyond the respective sides of the shaft and operative to maintain the said frame con- .and resilient equalizing means simultaneousstantly in correct screening position during its positive gyration 9. A screening apparatus comprising a screen frame, a drive shaft having its axis substantially coincident with the center of,

gravity of said frame, stationary bearings for said shaft, counterweighted fly wheels on said shaft having annular bearings therein eccentric to the axis of the shaft, a hollow shaft freely encircling the drive shaft and seated in said annular bearings, said; hollow shaft carrying the screen frame, whereby during the rotation of the drive shaft the said hollow shaft and frame are'positively gyrated in circular paths lying in planes at right angles to the drive shaft, and resilient equalizing means simultaneously acting in the same direction upon said frame beyond the I respective sides of the shaft and operative to maintain'the said frame constantly in correct screening position during its positive gyration.

screen frame, a gyratory carrierelement therefor, a drive shaft having its axis substanti ally coincident with the center of gravity of said frame, stationary bearings for said shaft, means operated by said shaftto gyrate the said carrier element and frame in circular paths-lying in planes at right angles to the drive -'shaft,'and leaf springs supported ad,-

jacent to and longitudinally of the frame, the

10. A screening apparatus comprising a ends of said springsbeing connected to the frame at points spaced from the respective.

sides of the drive shaft and simultaneously acting in the same direction upon said frame to maintain the frame constantly in correct screening position during its positive gyration.

- 11. A screening apparatus comprising a screen frame, a carrier element therefor, a drive shaft having its axis substantially coincident with the center of gravity of said frame, stationary bearings for, said shaft,. means operated by said shaft positively to' gyrate the said carrier element and frame in circular paths lying in planes atright angles to the drive shaft, an adjustable sup-porting element adjacent to the said frame, means for fixing said element. in positions of adjustment, and rin supported on said element and adjusta 1e t erewith, said springs-being arranged to act upon the frame at points spaced from the respective sides of the said shaft and" to act simultaneously in the same direction upon said frame to maintain the frame eonstantl in correct screening position during. its positive gyration. 12. A screening apparatus comprising a base structure, a screen frame, a carrier element for said frame, a drive shaft mounted on said structure and having its axis substantially coincident with the center of gravity of said frame, means operated by said shaft to ally mounted in the base structure, leaf springs secured at their mid sections to said frame and having link connections at their eritremities with the screen frame, means for adjusting said pendant frame, and means for securing "said pendant frame in positions of adjustment.

Signed at New York, in-the county and State of New York, this 11th dayjofA-pril',"

' A. D. 1927. v

' SAMUEL DAVIS ROBINS. 

